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22-07-2019 | Rheumatology | News | Article

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Partial knee replacement recommended for medial compartment osteoarthritis

medwireNews: Partial knee replacement (PKR) is more cost-effective than total knee replacement (TKR) over 5 years for patients with late-stage isolated medial compartment osteoarthritis of the knee, show results of the TOPKAT trial published in The Lancet.

Although both procedures offered similar clinical outcomes and “remain treatment options for late-stage medial compartment arthritis of the knee,” David Beard (University of Oxford, UK) and co-authors recommend that PKR should “be considered the first-choice procedure (based on 5-year outcomes)” in these patients.

The researchers report that, at 5 years after surgery, the Oxford Knee Score (OKS) had improved from 18.8 to 38.0 in the 264 patients randomly assigned to undergo PKR and from 19.0 to 37.0 in the 264 assigned to TKS. This resulted in a nonsignificant mean difference of 1.0 point, which was below the minimally important clinical difference of 2.0 points set by the researchers at the time of study planning and “well within the more recently accepted minimally important difference in OKS (now set at 5 points),” they remark.

There was also no significant difference between PKR and TKR in the proportion of patients undergoing reoperations (6 vs 8%) and revisions (4% for both) nor in patient satisfaction levels at 5 years, but the EQ-5D quality of life visual analog score was significantly higher (75.4 vs 71.7) and the complication rate significantly lower (20 vs 27%) in the PKR group than in the TKR group at 5 years. Beard and team note that the most common complications were unexplained pain, knee stiffness, or both.

A cost-effectiveness analysis (based on UK prices in 2017) revealed that PKR was more effective than TKR, providing 0.240 additional quality-adjusted life-years (QALYs), and was £910 (US$ 1135, € 1011) less expensive than TKR during the 5 years of follow-up.

The investigators say that this was due to a better outcome, as measured by QALYs derived from EQ-5D scores and survival, lower costs of PKR surgery, and lower follow-up health-care costs with PKR than TKR.

“Even assuming equal costs of the implant device, PKR was less costly and more effective than TKR,” they remark.

Beard et al conclude: “Our 5-year study has indicated that both TKR and PKR are beneficial interventions but, based on our combined clinical and cost-effectiveness data and providing the operation is performed by those with adequate experience, we recommend that PKR should be offered as the treatment of choice for late-stage isolated medial compartment osteoarthritis of the knee.”

In an accompanying comment, Jonathan Evans and Michael Whitehouse, both from Southmead Hospital in Bristol, UK, say that the “valuable study adds strength to previous data, which suggested no difference in clinical outcomes between PKR and TKR.”

However, they question whether the improved cost-effectiveness “will be sustained beyond 5 years.”

The commentators say: “As more implants are revised over time, the relative cost-effectiveness could change; thus, we await the long-term results with interest.”

By Laura Cowen

medwireNews is an independent medical news service provided by Springer Healthcare. © 2019 Springer Healthcare part of the Springer Nature group

Lancet 2019; doi:10.1016/S0140-6736(19)31281-4
Lancet 2019; doi:10.1016/ 10.1016/S0140-6736(19)31612-5

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